metallo enzymes- b.sc semester-6 ,epoenzymes ,coenzymes ,substrate ,carbonic anhydrase ,carboxy peptidase

1. Metallo-enzymes
CECH-612
UNIT-4(A)
BY - Ms MAYURI R SOMPURA

2. INTRODUCTION :-
• Enzymes are catalysts for biological systems.
• Their basic structure is built of protiens.
• Enzymes which are composed of a protein structure are called a
epoenzymes.
• They have a small prosthetic group which may be simple or a
complexed metal ion.
• Coenzyme – a group that combines reversibly with an enzyme for a
particular reaction and is released to combine with other enzymes is
known as coenzyme.
• The prosthetic groups and coenzymes are called as cofactors.
BY - Ms MAYURI R SOMPURA

3. INTRODUCTION :-
• More than 1500 metalloenzymes are identified so far.
• Their names are derived by adding ‘ase’ to the name of process
catalyzed of to the name of molecules on which the enzyme acts.
• The molecules on which the enzyme acts is called the substrate.
BY - Ms MAYURI R SOMPURA

4. BY - Ms MAYURI R SOMPURA
Sr no. Name of metalloenzyme Metal present
1
I. Phosphohydrolases
II. phosphotransferases
Magnesium
2
I. Cytochromes
II. peroxidases catalases
III. ferridoxine
Iron
3
I. Tryosinase,
II. amine oxidase
III. cytochrome oxidase
IV. ascorbate oxidase
V. galactose oxidase
Copper
4
I. Arginase
II. oxaloacetone decarboxylase
Manganese
5
I. Alcohol dehydrogenase
II. alkaline phosphatase
III. carbonic anhydrae
IV. carboxy peptidase
Zinc
4 I. Nitrogenase Iron and molybdenum

5. CARBONIC ANHYDRASE:-
• It is a zinc enzyme.
• Catalyse hydration of carbon dioxide and dehydration of carbonic
acid.
• It can hydrate 106 molecules of carbon dioxide at 37℃ which is about
107 times faster than the uncatalysed rate of hydration of carbon
dioxide.
• It has a molar mass of 30,000
• It occurs in animals as well as plants.
BY - Ms MAYURI R SOMPURA

6. CARBONIC ANHYDRASE:-
• The zinc iron lies in a deep pocket created by the coiled epoenzymes
• Coordinated with three nitrogen atoms of three imidazole rings of
histidine groups of epoenzyme.
• The fourth coordination iste is occupied with water molecule when
the enzyme is at rest.
• The stereochemistry of zinc in the enzyme is tetrahedral.
BY - Ms MAYURI R SOMPURA

7. CARBONIC ANHYDRASE:-
BY - Ms MAYURI R SOMPURA

8. CARBONIC ANHYDRASE:-
BY - Ms MAYURI R SOMPURA

9. CARBOXY PEPTIDASE:-
• It is also a zinc enzyme.
• It hydrolyses the terminal peptide bond of the peptide chain from the
side of its carboxy end.
• Example :-
BY - Ms MAYURI R SOMPURA

10. CARBOXY PEPTIDASE:-
• This enzyme is selective.
• It hydrolyses those polypeptides in which the terminal amino acid
segment has an aromatic or branched chain aliphatic substituent R’’
• tn this enzyme, metal ion is bonded to two imidazoles of histidine
group and a glutamic acid residue of the epoenzyme.
• A water molecule is weakly bonded to thr fourth coordination site of
Zn+2 ion when the enzyme is at rest.
• The active Zn+2 ions located at the depression formed on the surface
of the coiled epoenzyme.
• Close too this depression there is an empty pocket formed by the
coiled epoenzyme for accommodating the substrate.
BY - Ms MAYURI R SOMPURA

11. CARBOXY PEPTIDASE:-
• This enzyme is belived to act through the displacement of the
coordinated water by the C=O group of the terminal amide linkage of
the substrate.
BY - Ms MAYURI R SOMPURA

12. CARBOXY PEPTIDASE:-
• It has been established that the Zn+2 ions can be replaced by Co+2
ions with the retention of the enzyme activity.
• Since Zn+2 id a d10 system, the zinc enzyme does not give d-d
electron absorption bands in the visible region.
• The cobalt enzyme would show absorption bands in the visible region
due to d-d transitions from which the valuable information about metal
ion environment can be obtained .
BY - Ms MAYURI R SOMPURA